In 1982, more than one-fourth of the children living in poverty were not covered by Medicaid (Title XIX of the Social Security Act). As a result, Congress is considering legislation to extend Medicaid coverage to uninsured low income children. The impact of Medicaid on pediatric utilization is an empirical question. Previous studies suggest that Medicaid coverage increases overall physician use while reducing the use of office-based physicians. Nevertheless, most of the studies are of limited utility for current policy debates due to the population of inference: they usually include children of all incomes, not only low income children; many cover a narrow geographic area, and are not generalizable to the U.S. population; and most are based on data now 10 to 15 years old. The proposed research examines physician utilization for a national sample of low income children, emphasizing the effect of Medicaid coverage. Data for the study are from the 1980 National Medical Care Utilization and Expenditure Survey. The sample for this study will be restricted to children under age 17 in families with incomes below 150 percent of the federal poverty level in 1980. Both descriptive and multivariate analyses will be conducted. First, the low income children on Medicaid will be compared to thos not on Medicaid, with respect to socio-economic characteristics and utilization patterns. This descriptive analysis will be based on frequency distributions and crosstabulations. The multivariate analysis has two specific aims. The first is to assess the relative importance of a variety of factors, including Medicaid, on pediatric utilization. An economic model of health service use will be operationalized and tested (using regression procedures) against a series of utilization indices. The second aim is to determine the extent and direction of utilization differences between Medicaid and non-Medicaid children, controlling for other factors that have been shown to affect use. Smoothed contingency table analysis will be employed. The research has two long-term objectives: (1) to assist policy-makers in assessing the potential effectiveness of alternate strategies for influencing physician utilization among low income children; and (2) to inform policymakers of the effect of Medicaid coverage on mulitple measures of physican use.